The director of the US Secret Service has resigned in the face of revelations of security breaches and an erosion of confidence over the safety of President Barack Obama and his family.
Julia Pierson offered her resignation after it emerged that a man armed with a knife had made it past security staff at the White House.
Once highly respected for its professionalism, the Secret Service, which protects the President, his family, the Vice President and former presidents, has been trying to rehabilitate its image since a 2012 prostitution scandal erupted during a presidential visit to Colombia.
That trust was shaken by a series of failures in the agency's job of protecting the President, including a breach on September 19, when a knife-carrying man climbed over the White House fence and made it deep into the executive mansion before being stopped.
Mr Obama “concluded new leadership of that agency was required,” said White House spokesman Josh Earnest.
A White House official said the final straw was the revelation that Mr Obama was never briefed about an incident in which he rode a lift with an armed security contractor during a visit to the Centres for Disease Control and Prevention in Atlanta, just days before the White House breach.
Although Julia Pierson offered her resignation without being asked, Mr Obama had already told aides he thought she should go, the official said, adding that nobody put up any resistance when she offered to step down.
Both Republican and Democratic figures had urged Ms Pierson to step down after her poorly received testimony to Congress a day earlier - and revelation of yet another security problem: Mr Obama had shared a lift in Atlanta last month with an armed guard who was not authorised to be around him.
That appeared to be the last straw that crumbled trust in her leadership in the White House. Mr Earnest said Mr Obama and his staff did not learn about that breach until just before it was made public in news reports Tuesday.
Homeland Security Secretary Jeh Johnson said Joseph Clancy, retired head of the agency's Presidential Protective Division, would come out of retirement to lead the Secret Service temporarily.
Taking further steps to restore trust in the beleaguered agency, Mr Johnson also outlined an independent inquiry into the agency's operations.
Republicans quickly served notice that Ms Pierson's resignation and the inquiry ordered by Mr Johnson would not end their investigation.
“Problems at the Secret Service pre-date Ms Pierson's tenure as director, and her resignation certainly does not resolve them,” said Darrell Issa, the Republican chairman of the House Oversight Committee.
In an interview with Bloomberg after her resignation was announced, Pierson said: “It's painful to leave as the agency is reeling from a significant security breach.
“Congress has lost confidence in my ability to run the agency. The media has made it clear that this is what they expected.”
The man accused of running into the White House on September 19, Omar J Gonzalez, pleaded not guilty in a federal court to a charge of unlawfully entering a restricted building while carrying a deadly weapon and two violations of District of Columbia law - carrying a dangerous weapon outside a home or business and unlawful possession of ammunition.
Wearing a standard prison-issue orange jump suit, Gonzalez did not address the court as his lawyer entered the plea.